1. Field of the Invention
The present invention relates generally to valves with rotating stems carrying fluids under pressure and, more particularly, to novel valve cap assemblies for use on such valves.
2. Discussion
A number of known types of valves, such as ball valves, for example, carrying fluids under pressure employ rotatable valve stems as a means of operating the valves. More specifically, the flow of fluid through such a valve may be controlled by the rotation of its stem by a tool.
Such valves typically employ a valve body through which a fluid passageway extends. The valve stem passes through a separate passageway, or valve stem passageway, in the valve body. Since one end of the valve stem protrudes from the exterior of the valve body, to allow manipulation, and the other end connects to the flow control means in the interior fluid passageway, the valve stem passageway must extend from the exterior of the valve body through to the fluid passageway within the valve body. As such, a valve stem seal, often consisting of an O-ring, is employed to seal the valve stem passageway as well as to provide a bearing for resisting the internal pressure load acting on the valve stem.
If the valve stem seal fails, internal pressure will force the fluid being carried by the valve through the valve stem passageway to the exterior of the valve body. Depending on the nature of the valve stem seal failure, the fluid may either drip, flow or spray out of the valve body. This leakage could easily cause damage to surrounding components or create hazardous conditions. To guard against such a result, valve caps of known type are typically placed upon the valves so as to provide a sealed cover around the valve stem and valve stem passage opening in the valve body. Should valve stem seal failure occur when such a valve cap is in place, the fluid leakage will be contained within the valve cap.
Manipulation of a valve utilizing such a valve cap requires the removal of the valve cap for access to the valve stem. This takes additional time, effort and tools. Removed valve caps could also be lost, misplaced or not replaced through error. In addition, repeated removals and replacements of a cap can cause the cap seal itself to wear prematurely. For these and other reasons there is a chance of fluid leakage from the valve cap.
It is, therefore, an object of the present invention to provide a valve cap in combination with an external valve stem drive that together allow manipulation of the valve stem without removal of the valve cap or endangerment of the valve cap seal.